Registry settings through Group Policy?

I need to make a registry change for every single machine in my domain, but it’s not a setting currently covered in the GPO (that I can see).

I want to set the advanced power settings so that all the power settings are set to “NEVER” (The “PRESENTATION” power scheme).

Since I’m asking this, can anyone explain how I’d add any other custom registry keys using GPO?

I cannot figure out how to do this. Help!